A conductive paste is a paste in which metal particles which are conductive are dispersed in a resin, etc. Since silver powder is highly electrically conductive and resists oxidation, silver powder is commonly used as the conductive material.
The conductive pastes are mainly classified into firing type conductive pastes and polymer type conductive pastes. The firing type conductive pastes develop conductivity by heating to about 500 to 900° C., and thereby metal particles are sintered to each other and a continuous conductive layer can be obtained. The polymer type conductive paste contains resin, in order to improve coating properties, dispersing properties of metal particles, and adhesion to a substrate. When the polymer type conductive paste is heated from about room temperature to 200° C., the resin is cured. The resin is cured and the metal particles are contacted to each other at the same time, a continuous conductive film is prepared and conductivity is thereby established. Since the polymer type conductive paste is heated to a temperature lower than that in the firing type conductive paste, and this requires energy for preparing a conductive film, which is lower than that in the firing type conductive paste, the polymer type conductive paste can reduce the production cost of a conductive film.
However, since the polymer type conductive paste contains resin, when this is heated and cured, resin, which is an insulating material, intervenes between metal particles, and metal particles cannot be sintered to each other, and it is thereby impossible to sufficiently decrease electrical resistance of the conductive film. In addition, when resin is not contained in the conductive paste, a conductive paste having a sufficient viscosity for coating easily cannot be obtained.
In consideration of the above-described problems, an object of the present invention is to provide a silver compound paste which is easily applied even if no resin is contained, and in which metal particles are sintered and continuously even if it is heated to a temperature substantially equal to a temperature in the polymer type conductive paste, and which can produce a conductive film having a low electric resistivity.